The present invention relates generally to tractor hitches and more particularly to a hitch configuration in which visiblity of the tractor to implement connectors, the ease of coupling to an implement, ease of use, versatility, performance and total vehicle design styling has been maximized.
In the past, visibility of the couplers on the three-point hitch and the drawbar connector was not a significant problem. The operator on a standard sized tractor was so close to the hitch that neither the rockshaft housing nor the center link on the three-point hitch presented a significant obstruction to the operator's line of sight. The rockshaft was positioned high on the tractor body and the center link was connected along the fore and aft center line of the tractor near the rockshaft.
As tractors have become larger, the old hitch configuration has continued to be used with mere structural upgrading. As the huge four wheel drive articulated tractors have evolved, this has resulted in a sacrifice in the ability to directly observe the tractor to implement connection. Some manufacturers have used the expedients of mirrors or even closed-circuit television cameras to observe the hitch area. Heretofore, no serious consideration has been given to changing the hitch configuration to maximize visibility for the even larger tractors which are expected in the future or of utilizing an improved hitch configuration on standard sized tractors to replace the current hitches.
Also in the past, it was expected that implements which were too heavy to be moved manually would be connected by judiciously maneuvering the tractor into position next to the implement and lifting the hitch. If the implement would not move into hitching position, the hitch would be lowered and the tractor would have to be moved again and the hitching operation tried again. This trial and error positioning was also required for connecting a drawbar implement to the drawbar connector. Thus, tractor operators generally had to have a high level of skill.
Another practice in the past was to have the draft link convergence, or the intersection in the tractor body of the forces applied at the rear ends of the draft links, to be at the front axle. This was to assure that when the front wheels were turned for steering on a two-wheel drive tractor, the hitch would cause the implement to follow the front wheels into a turn. This principle was retained with the advent of four-wheel drive articulated tractors since those skilled in the art believed that the implement should follow the front wheels.
In the early four-wheel drive tractors, it was quickly discovered that abrupt steering changes would often cause failures of the hitch components on the implements because of the imposition of large lateral loads because the rear axle to which the implement was secured would "wiggle" relative to the front axle. In more recent tractors, these failures which are a symptom of the excessively large lateral loads were treated by preventing the tractor from making abrupt steering changes, which is a case of treating the sympton rather than the problem.
In conventional two and four wheel drive tractors, sway and anti-sway control is achieved primarily by repositionable sway blocks which are located near the forward end of the draft links. As larger tractors have drawn larger implements, larger lateral operational loads have been imposed on the rear ends of the draft links requiring that the draft links be increased in size to increase strength. This increase in size has generally been detrimental to overall tractor styling.